A Comparison of High-Frequency Oscillation Superimposed onto Backup Mechanical Ventilation and Conventional Mechanical Ventilation on the Distribution of Exogenous Surfactant in Premature Lambs

摘要

Twenty-six premature iambs were treated by traeheal instillation [14C]labeled natural sheep surfactant before the onset of breathing or after the establishment of respiratory distress syndrome 30 min after birth. Half of both groups were subsequently ventilated for 3 h with 100% O2 by conventional mechanical ventilation (CMV) and half by high frequency oscillation superimposed onto backup mechanical ventilation (HFOV). Mean airway pressure, arterial blood pressures, and heart rate were recorded continuously. Arterial blood gases and pH were obtained every 15 min. After sacrifice, the distribution of radiolabeled surfactant was quantified and alveolar expansion was evaluated by morphometrics. At comparable oxygenation, mean airway pressures were significantly lower in the lambs treated with surfactant at birth (groups CMVB and HFOV-B) than in lambs on CMV and treated with surfactant during RDS (group CMV-R). Mean airway pressures in both groups of lambs on HFOV (groups HFOV-B and HFOV-R) were comparable at values lower than in group CMV-R and higher than in group CMV-B. The distribution of radiolabeled surfactant was more homogeneous in lambs treated at birth and not different for both types of ventilatory assistance. Morphometrics demonstrated significantly better expansion of the alveoli of lambs ventilated with HFOV than of those on CMV, irrespective of the timing of surfactant administration. These results indicate that prophylactic surfactant administration at birth leads to a better distribution of surfactant than rescue treatment with surfactant after the establishment of respiratory distress syndrome and is not affected by a subsequent type of ventilatory assistance. Rescue treatment with surfactant and subsequent HFOV leads to better oxygenation and alveolar expansion at comparable mean airway pressures than rescue treatment followed by CMV.